SED1MENTOLOGICAL FACIES ANALYSIS AND SEQUENCE STRATIGRAPHY OF PERMIAN COALBEARING FLU VIO-MARINE INTERACTIVE SYSTEM, WEST BOKARO BASIN, INDIA

Abstract

The upper part of the coal-bearing Barakar Formation (early Permian) of the West Bokaro Basin was previously interpreted as continental fluvial sediments with little evidence for tide-wave influences. The present detailed study has found the attributes of marginal marine tidal and wave activities preserved within an overall braided-meandering fluvial depositional setting. The present study is carried out along a road section (NH-33) connecting Ranchi and Hazaribagh in Jharkhand, India. A succession of almost seventy meters thick sediments along this highway section beginning at 23° 44' 12.9" N 085 30' 10.2" E and ending at 230 44'45.0" N 085 30'0 1 .0"E was detailed and measured. The facies association represented an overall fluvial channel system in the lower part that develops into a fluvio-marine interactive system with the interdistributary flood plain deposits in the upper part. Nine major fades were identified. Petrographic studies from few samples also concurred such interpretations about the environment of deposition. Further, sequence stratigraphic analyses of the strata pointed out major sequence boundaries and bounding sufaces. Also with the help of parasequence stacking patterns we could interpret the timeline of events related to major eustatic sea-level changes. More detailed interpretation with the help of the delineated system tracts helped us to interpret the basinal conditions under which the strata was deposited and it pointed to a shelf-like setting namely- filled foreland basins or intercratonic basins